In recent years, further miniaturization and higher functionalization of solid-state imaging devices have been seen. In connection with this, more and more solid-state imaging devices have been mounted on portable equipment such as mobile telephones and portable computers, and on motorcars, and as a result, the application field of these devices has been becoming wider and wider. One of the application fields of solid-state imaging devices is a digital camera; high image-quality digital single-lens reflex cameras using solid-state imaging devices have been put into practical use.
With such high image-quality digital cameras as described above, imaging operation is performed by converting external light incident on the imaging region of an imaging element by way of an imaging optical system such as a collecting lens into electric signals. Usually, the imaging optical system is located in a tubular lens receiving member (lens barrel), by which unnecessary external light is prevented from entering the imaging region.
The aforementioned solid-state imaging element comprises a transparent cover that covers the imaging region. Here, a region of the cover that corresponds to the imaging region is termed a “transmission section”, and another region of the cover that is outside the “transmission section” is termed an “edge section”. External light transmitted through the imaging optical system can enter the imaging region, if it passes through the transmission section; however, if it passes through the edge section, the external light does not enter the imaging region. For this reason, by setting the opening of the lens receiving member such that external light that has passed through the imaging optical system is transmitted only through the transmission section of the cover, the solid-state imaging device can be structured in such a way that only external light that has passed through both of the imaging optical system and the transmission section enters the imaging region. Here, external light that has passed through the imaging optical system and the transparent cover and directly entered the imaging region (without reflection at other positions) is termed “direct incident light”.
By the way, as a technique for improving the image quality by preventing incidence of unnecessary light to the imaging region, various techniques have ever been developed and published.
For example, the Patent Literature 1 (Japanese Unexamined Patent Publication No. 2004-140497) discloses a camera module comprising a light intercepting wall that extends around the entire periphery of a connecting portion between a lens barrel (which incorporates a colleting lens) and a package body in order to block external light (unnecessary light) that is incident through gaps formed at other positions than the bonding spots between the lens barrel and the package body, thereby preventing such the unnecessary light from entering the imaging region of a solid-state imaging element. (See FIGS. 1 and 2 and Abstract.)
The Patent Literature 2 (Japanese Unexamined Patent Publication No. 2005-109092) discloses a solid-state imaging device comprising light receiving pixels, a microlens array whose microlenses are arranged two-dimensionally within at least a range including these light receiving pixels corresponding to the respective light receiving pixels, and a transparent member (a transparent cover) placed on the incidence side of the microlens array. A protruding part is formed to be integral with the transparent member on the opposing side of this member to the microlens array at a position that does not overlap with the light receiving pixels. The transparent member is supported by this protruding part. The protruding part surrounds the light receiving pixels like a picture frame, and is formed higher than the height of the microlens array. In this way, an air layer is formed between the transparent member and the microlens array.
Coating for blocking infrared light (infrared-light cut coating) is applied to the incidence side of the aforementioned transparent member. A light-blocking section is formed by light-tight printing or the like outside the region through which a pencil of light of an object (external light) sent from the imaging optical system penetrates.
The Patent Literature 2 discloses an imaging apparatus equipped with the solid-state imaging device having the aforementioned structure also. This imaging apparatus comprises the aforementioned imaging device, and an outer frame member incorporating the imaging optical system (first and second lenses) that forms an image of an object on this imaging device. A compression coil spring is incorporated into the outer frame member. The top end opening of the outer frame member is covered with a lid member.
With the solid-state imaging device of the Patent Literature 2, because of the aforementioned structure, the surface of the microlens array (the imaging region) is sealed with the transparent member from the initial step of the fabrication process sequence of the aforementioned imaging apparatus and therefore, the surface of the microlens array can be protected from moisture and dust. Accordingly, the fabrication yield reduction due to dust adhesion during the fabrication process sequence can be minimized, which makes it possible to reduce the cost through improvement of the quality product rate. (See FIGS. 1 to 4, Paragraphs 0045 to 0065 and 0105 to 0106, and Abstract.)
The Patent Literature 3 (Japanese Unexamined Patent Publication No. 2001-274370) discloses a package for a light receiving element that prevents false signals, and a solid-state imaging device that reduces flare. This package comprises a container having a cavity for storing a light-receiving element, and internal terminals for electrical connection to the light-receiving element, wherein the container is sealed with an optically transparent cover. Between the cavity and the cover, a light-blocking member having an opening that leads incident light and a tapered part that blocks stray light is located. The tapered part of the light-blocking member is formed in the peripheral area of this member to surround the opening thereof. Since the opening is located to be superposed on the light-receiving region of the light-receiving element, the tapered part is located to surround the light-receiving region. Preferably, an optical absorption layer formed by a black paint, Kinguro, or the like is formed on the light-blocking member.
With the package for a light receiving element of the Patent Literature 3, by the aforementioned structure, light that has obliquely penetrated through the transparent cover to enter the inside of the container (oblique incident light) is blocked by the light-blocking member. For this reason, there is no possibility that the oblique incident light is reflected on the surface of the light-receiving element and scattered by the metal thin lines connecting electrically the light-receiving element to the internal terminals, the inner face of the container, or the like, thereby inducing scattered light. Accordingly, false signals caused by incidence of the scattered light on the light-receiving region of the light-receiving element are prevented from occurring. If the optical absorption layer is formed on the light-blocking member, the scattered light irradiated to this light-blocking member is absorbed by the optical absorption layer; therefore, the false signal preventing effect can be enhanced.
With the solid-state imaging device of the Patent Literature 3, a solid-state imaging element is mounted on the aforementioned package for a light-receiving element instead of the light-receiving element. Flare caused by incidence of the scattered light on the imaging region of the solid-state imaging element is prevented from occurring by the light-blocking member. (See claims 1 and 8, FIGS. 1 to 2 and 11, Paragraphs 0014 to 0018 and 0043 to 0053.)
The Patent Literature 4 (Japanese Unexamined Patent Publication No. 2006-41277) discloses a solid-state imaging device comprising a solid-state imaging element provided on one surface of a semiconductor substrate, and a transparent plate (a cover glass) that seals the upper side of this element and that has end faces approximately tapered toward the upper surface from the lower surface. With this device, The end faces of the cover glass are tapered and therefore, reflected light, which is generated by oblique incidence of light on the end faces of the cover glass and reflection thereon and which reaches the solid-state imaging element, does not exist. Accordingly, noises due to the aforementioned reflected light can be reduced similar to the case where anti-reflection films are provided on the end faces. (See claim 3, FIGS. 10 to 11, Paragraphs 0043 to 0044.)
The Patent Literature 4 further discloses a solid-state imaging device comprising a cover glass that has end faces on which anti-reflection films are provided instead of the tapered end faces, and another solid-state imaging device comprising a cover glass whose end faces are roughened instead of providing the anti-reflection films. (See claim 1, FIGS. 1 to 3 and FIGS. 12 to 13, Paragraphs 0030, 0046 to 0047.)    Patent Literature 1: Japanese Unexamined Patent Publication No. 2004-140497    Patent Literature 2: Japanese Unexamined Patent Publication No. 2005-109092    Patent Literature 3: Japanese Unexamined Patent Publication No. 2001-274370    Patent Literature 4: Japanese Unexamined Patent Publication No. 2006-41277